On 2020-Apr-01, Jürgen Purtz wrote: > > On 31.03.20 19:58, Justin Pryzby wrote: > > On Tue, Mar 31, 2020 at 04:13:00PM +0200, Jürgen Purtz wrote: > > > Please find some minor suggestions in the attachment. They are based on > > > Corey's last patch 0001-glossary-v4.patch. > > > @@ -220,7 +220,7 @@ > > > Record</glossterm>s to the file system and creates a special > > > checkpoint record. This process is initiated when predefined > > > conditions are met, such as a specified amount of time has > > > passed, or > > > - a certain volume of records have been collected. > > > + a certain volume of records has been collected. > > I think you're correct in that "volume" is singular. But I think > > "collected" > > is the wrong world. I suggested "written". > > > "collected" is not optimal. I suggest "created". Please avoid "written", the > WAL records will be written when the Checkpointer is running, not before.
Actually, you're mistaken; the checkpointer hardly writes any WAL records. In fact, it only writes *one* wal record, which is the checkpoint record itself. All the other wal records are written either by the backends that produce it, or by the wal writer process. By the time the checkpoint runs, the wal records are long expected to be written. Anyway I changed a lot of terms again, as well as changing the way the terms are marked up -- for two reasons: 1. I didn't like the way the WAL-related entries were structured. I created a new entry called "Write-Ahead Log", which explains what WAL is; this replaces the term "WAL Log", which is redundant (since the L in WAL stands for "log" already). I kept the id as glossary-wal, though, because it's shorter and *shrug*. The definition uses the terms "wal record" and "wal file", which I also rewrote. 2. I found out that "see xyz" and "see also" have bespoke markup in Docbook -- <glosssee> and <glossseealso>. I changed some glossentries to use those, removing some glossdefs and changing a couple of paras to glossseealsos. I also removed all "id" properties from glossentries that are just <glosssee>, because I think it's a mistake to have references to entries that will make the reader look up a different term; for me as a reader that's annoying, and I don't like to annoy people. While at it, I again came across "analytic", which is a term we don't use much, so I made it a glosssee for "window function"; and while at it I realized we didn't clearly explain what a window was. So I added "window frame" for that. I considered adding the term "partition" which is used in this context, but decided it wasn't necessary. I also added "(process)" to terms that define processes. So now we have "checkpointer (process)" and so on. I rewrote the definition for "atomic" once again. Made it two glossdefs, because I can. If you don't like this, I can undo. I added "recycling". I still have to go through some other defs. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
diff --git a/doc/src/sgml/filelist.sgml b/doc/src/sgml/filelist.sgml index 1043d0f7ab..cf21ef857e 100644 --- a/doc/src/sgml/filelist.sgml +++ b/doc/src/sgml/filelist.sgml @@ -170,6 +170,7 @@ <!ENTITY limits SYSTEM "limits.sgml"> <!ENTITY acronyms SYSTEM "acronyms.sgml"> +<!ENTITY glossary SYSTEM "glossary.sgml"> <!ENTITY color SYSTEM "color.sgml"> <!ENTITY features-supported SYSTEM "features-supported.sgml"> diff --git a/doc/src/sgml/glossary.sgml b/doc/src/sgml/glossary.sgml new file mode 100644 index 0000000000..3c417f2fd3 --- /dev/null +++ b/doc/src/sgml/glossary.sgml @@ -0,0 +1,1526 @@ +<appendix id="glossary"> + <title>Glossary</title> + <para> + This is a list of terms and their meaning in the context of + <productname>PostgreSQL</productname> and relational database + systems in general. + </para> + + <glosslist> + <glossentry id="glossary-aggregating"> + <glossterm>Aggregating</glossterm> + <glossdef> + <para> + The act of combining a collection of data (input) values into + a single output value, which may not be of the same type as the + input values. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-aggregate"> + <glossterm>Aggregate Function</glossterm> + <glossdef> + <para> + A <glossterm linkend="glossary-function">function</glossterm> that + combines multiple input values, + for example by counting, averaging or adding them all together, + yielding a single output value. + </para> + <para> + For more information, see + <xref linkend="functions-aggregate"/>. + </para> + <glossseealso otherterm="glossary-window-function" /> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Analytic Function</glossterm> + <glosssee otherterm="glossary-window-function" /> + </glossentry> + + <glossentry id="glossary-atomic"> + <glossterm>Atomic</glossterm> + <glossdef> + <para> + In reference to a <glossterm linkend="glossary-datum">datum</glossterm>: + the fact that its value that cannot be broken down into smaller + components. + </para> + </glossdef> + <glossdef> + <para> + In reference to a + <glossterm linkend="glossary-transaction">database transaction</glossterm>: + the fact that all the operations in the transaction either complete as + a whole, or none of them become visible. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-atomicity"> + <glossterm>Atomicity</glossterm> + <glossdef> + <para> + One of the <acronym>ACID</acronym> properties. This is the state of + being <glossterm>Atomic</glossterm> in the operational/transactional sense. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-attribute"> + <glossterm>Attribute</glossterm> + <glossdef> + <para> + An element with a certain name and data type found within a + <glossterm>Tuple</glossterm> or <glossterm>Table</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-autovacuum"> + <glossterm>Autovacuum</glossterm> + <glossdef> + <para> + Background processes that routinely perform + <glossterm>Vacuum</glossterm> and <glossterm>Analyze</glossterm> + operations. + </para> + <para> + For more information, see + <xref linkend="routine-vacuuming"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-backend-process"> + <glossterm>Backend Process</glossterm> + <glossdef> + <para> + Processes of an <glossterm>Instance</glossterm> which act on behalf of + client <glossterm>Connection</glossterm>s and handle their requests. + </para> + <para> + (Don't confuse this term with the similar terms + <glossterm>Background Worker</glossterm> or + <glossterm>Background Writer</glossterm>). + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-background-worker"> + <glossterm>Background Worker</glossterm> + <glossdef> + <para> + Individual processes within an <glossterm>Instance</glossterm>, which + run system- or user-supplied code. A typical use case is a process + which handles parts of an <acronym>SQL</acronym> query to take + advantage of parallel execution on servers with multiple + <acronym>CPU</acronym>s. + </para> + <para> + For more information, see + <xref linkend="bgworker"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-background-writer"> + <glossterm>Background Writer</glossterm> + <glossdef> + <para> + A process that continuously writes dirty pages from + <glossterm>Shared Memory</glossterm> to the file system. + It wakes up periodically, but + works only for a short period in order to distribute its expensive + <acronym>I/O</acronym> activity over time, instead of generating fewer + larger <acronym>I/O</acronym> peaks which could block other processes. + </para> + <para> + For more information, see + <xref linkend="runtime-config-resource"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-cast"> + <glossterm>Cast</glossterm> + <glossdef> + <para> + A conversion of a <glossterm>Datum</glossterm> from its current data + type to another data type. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-catalog"> + <glossterm>Catalog</glossterm> + <glossdef> + <para> + The <acronym>SQL</acronym> standard uses this term to + indicate what is called a <glossterm>Database</glossterm> in + <productname>PostgreSQL</productname>'s terminology. + </para> + <para> + This should not be confused with the + <glossterm>System Catalog</glossterm>. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-check-constraint"> + <glossterm>Check Constraint</glossterm> + <glossdef> + <para> + A type of <glossterm>Constraint</glossterm> defined on a + <glossterm>Relation</glossterm> which restricts the values allowed in + one or more <glossterm>Attribute</glossterm>s. The <glossterm>Check + Constraint</glossterm> can make reference to any + attribute in the + <glossterm>Relation</glossterm>, but cannot reference other + <glossterm>Row</glossterm>s of the same + relation or other relations. + </para> + <para> + For more information, see + <xref linkend="ddl-constraints"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-checkpointer"> + <glossterm>Checkpointer (process)</glossterm> + <glossdef> + <para> + A process that writes dirty pages to the file system and creates a special + checkpoint WAL record. This process is initiated when predefined + conditions are met, such as a specified amount of time has passed, or + a certain volume of records has been collected. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-checkpoint"> + <glossterm>Checkpoint</glossterm> + <glossdef> + <para> + A point in time when all older dirty pages of the + <glossterm>Shared Memory</glossterm>, all older <glossterm>WAL Record</glossterm>s, + and a special <glossterm>Checkpoint record</glossterm> have been written + and flushed to disk. + </para> + <para> + For more information, see + <xref linkend="sql-checkpoint"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-cluster"> + <glossterm>Cluster</glossterm> + <glossdef> + <para> + A group of <glossterm>Database</glossterm>s plus their + <glossterm>Global SQL Object</glossterm>s. The + <glossterm>Cluster</glossterm> is managed by exactly one + <glossterm>Instance</glossterm>. A newly created + <glossterm>Cluster</glossterm> will have three + <glossterm>Database</glossterm>s created automatically. They are + <literal>template0</literal>, <literal>template1</literal>, and + <literal>postgres</literal>. It is expected that an application will + create one or more additional <glossterm>Database</glossterm>s aside + from these three. + </para> + <para> + Don't confuse the <productname>PostgreSQL</productname>-specific term + <glossterm>Cluster</glossterm> with the SQL command + <literal>CLUSTER</literal>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-column"> + <glossterm>Column</glossterm> + <glossdef> + <para> + An <glossterm>Attribute</glossterm> found in a + <glossterm>Table</glossterm> or <glossterm>View</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-commit"> + <glossterm>Commit</glossterm> + <glossdef> + <para> + The act of finalizing a <glossterm>Transaction</glossterm> within the + <glossterm>Database</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-commit"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-concurrency"> + <glossterm>Concurrency</glossterm> + <glossdef> + <para> + The concept that multiple independent operations happen within the + <glossterm>Database</glossterm> at the same time. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-connection"> + <glossterm>Connection</glossterm> + <glossdef> + <para> + An established line of communication between a client process + and a <glossterm>Backend Process</glossterm>. If the two involved processes reside on the + same <glossterm>Server</glossterm>, then the connection can either use + <acronym>TCP/IP</acronym> or Unix-domain sockets. Otherwise, + only <acronym>TCP/IP</acronym> can be used. + </para> + <para> + For more information, see + <xref linkend="runtime-config-connection"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-consistency"> + <glossterm>Consistency</glossterm> + <glossdef> + <para> + One of the <acronym>ACID</acronym> properties. This means that the database + is always in compliance with its own rules such as <glossterm>Table</glossterm> + structure, <glossterm>Constraint</glossterm>s, + <glossterm>Uniqueness</glossterm>, etc. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-constraint"> + <glossterm>Constraint</glossterm> + <glossdef> + <para> + A restriction on the values of data allowed within a + <glossterm>Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="ddl-constraints"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Data Area</glossterm> + <glosssee otherterm="glossary-data-directory" /> + </glossentry> + + <glossentry id="glossary-data-directory"> + <glossterm>Data Directory</glossterm> + <glossdef> + <para> + The base directory on the filesystem of a + <glossterm>Server</glossterm> that contains all data files and + subdirectories associated with a <glossterm>Cluster</glossterm> with + the exception of <glossterm>Tablespace</glossterm>s. The environment + variable <literal>PGDATA</literal> often — but not always — + refers to the <glossterm>Data Directory</glossterm>. + </para> + <para> + For more information, see + <xref linkend="storage-file-layout"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-database"> + <glossterm>Database</glossterm> + <glossdef> + <para> + A named collection of <glossterm>SQL Object</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Database Server</glossterm> + <glosssee otherterm="glossary-instance" /> + </glossentry> + + <glossentry id="glossary-datum"> + <glossterm>Datum</glossterm> + <glossdef> + <para> + The internal representation of one value of a <acronym>SQL</acronym> + data type. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-delete"> + <glossterm>Delete</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command which removes + <glossterm>Row</glossterm>s from a given <glossterm>Table</glossterm> + or <glossterm>Relation</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-delete"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-durability"> + <glossterm>Durability</glossterm> + <glossdef> + <para> + One of the <acronym>ACID</acronym> properties. This is the assurance that once a + <glossterm>Transaction</glossterm> has been <glossterm>Committed</glossterm>, the + data will remain even after a system failure or crash. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-file-segment"> + <glossterm>File Segment</glossterm> + <glossdef> + <para> + A physical file which stores data for a given + <glossterm>Heap</glossterm> or <glossterm>Index</glossterm> object. + <glossterm>File Segment</glossterm>s are limited in size by a + configuration value and if that size is exceeded, it will be split + into multiple physical files. + </para> + <para> + For more information, see + <xref linkend="storage-file-layout"/>. + </para> + <para> + (Don't confuse this term with the similar term + <glossterm>WAL Segment</glossterm>). + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-data-wrapper"> + <glossterm>Foreign Data Wrapper</glossterm> + <glossdef> + <para> + A means of representing data that is not contained in the local + <glossterm>Database</glossterm> so that it appears as if were in local + <glossterm>Table</glossterm>(s). With a Foreign Data Wrapper it is + possible to define a <glossterm>Foreign Server</glossterm> and + <glossterm>Foreign Table</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="sql-createforeigndatawrapper"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-key"> + <glossterm>Foreign Key</glossterm> + <glossdef> + <para> + A type of <glossterm>Constraint</glossterm> defined on one or more + <glossterm>Column</glossterm>s in a <glossterm>Table</glossterm> which + requires the value(s) in those <glossterm>Column</glossterm>s to + identify exactly one <glossterm>Row</glossterm> in another (or the same) + <glossterm>Table</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-server"> + <glossterm>Foreign Server</glossterm> + <glossdef> + <para> + A named collection of <glossterm>Foreign Table</glossterm>s which all + use the same <glossterm>Foreign Data Wrapper</glossterm> and have + other configuration values in common. + </para> + <para> + For more information, see + <xref linkend="sql-createserver"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-foreign-table"> + <glossterm>Foreign Table</glossterm> + <glossdef> + <para> + A <glossterm>Relation</glossterm> which appears to have + <glossterm>Row</glossterm>s and <glossterm>Column</glossterm>s similar + to a regular <glossterm>Table</glossterm>, but will forward requests + for data through its <glossterm>Foreign Data Wrapper</glossterm>, + which will return <glossterm>Result Set</glossterm>s structured + according to the definition of the <glossterm>Foreign Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createforeigntable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-function"> + <glossterm>Function</glossterm> + <glossdef> + <para> + Any defined transformation of data. Many functions are already defined + within <productname>PostgreSQL</productname> itself, but user-defined + ones can also be added. + </para> + <para> + For more information, see + <xref linkend="sql-createfunction"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-global-sql-object"> + <glossterm>Global SQL Object</glossterm> + <glossdef> + <para> + <glossterm>SQL Object</glossterm>s which do not belong to a specific + <glossterm>Schema</glossterm>. + </para> + <para> + Objects that exist at the <glossterm>Database</glossterm> level + include Extensions such as + <glossterm>Foreign Data Wrapper</glossterm>s. + </para> + <para> + Objects that exist at the <glossterm>Cluster</glossterm> level + include <glossterm>Role</glossterm>s, + <glossterm>Tablespace</glossterm>s, + <glossterm>Replication</glossterm> origins, and subscriptions + for logical replication. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-grant"> + <glossterm>Grant</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command that is used to allow + <glossterm>User</glossterm>s or <glossterm>Role</glossterm>s to access + specific objects within the <glossterm>Database</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-grant"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-heap"> + <glossterm>Heap</glossterm> + <glossdef> + <para> + Contains the values of <glossterm>Row</glossterm> attributes + (i.e. the data). The <glossterm>Heap</glossterm> is realized within + <glossterm>Database</glossterm> files. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Host</glossterm> + <glosssee otherterm="glossary-server" /> + </glossentry> + + <glossentry id="glossary-index"> + <glossterm>Index</glossterm> + <glossdef> + <para> + A <glossterm>Relation</glossterm> that contains data derived from a + <glossterm>Table</glossterm> (or <glossterm>Relation</glossterm> types + such as a <glossterm>Materialized View</glossterm>). Its internal + structure supports fast retrieval of and access to the original + data. + </para> + <para> + For more information, see + <xref linkend="sql-createindex"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-insert"> + <glossterm>Insert</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command used to add new data into a + <glossterm>Table</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-insert"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-instance"> + <glossterm>Instance</glossterm> + <glossdef> + <para> + An <glossterm>Instance</glossterm> is a group of processes plus their + common <glossterm>Shared Memory</glossterm> running on a single + <glossterm>Server</glossterm>. The <glossterm>Instance</glossterm> + handles all key features of a <acronym>DBMS</acronym>: read and write + access to files and shared memory, assurance of + the <acronym>ACID</acronym> paradigm, <acronym>MVCC</acronym>, + <glossterm>Connection</glossterm>s to client programs, backup, + recovery, replication, privileges, etc. + </para> + <para> + An <glossterm>Instance</glossterm> manages exactly one + <glossterm>Cluster</glossterm>. + </para> + <para> + Many <glossterm>Instance</glossterm>s can run on the same server as + long as their <acronym>TCP/IP</acronym> ports do not conflict. + Different instances on a server may use the + same or different versions of <productname>PostgreSQL</productname>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-isolation"> + <glossterm>Isolation</glossterm> + <glossdef> + <para> + One of the <acronym>ACID</acronym> properties. This means that concurrently running + <glossterm>Transaction</glossterm>s affect the database exactly as if they had been + executed sequentially. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-join"> + <glossterm>Join</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> keyword used in <command>SELECT</command> statements for + combining data from multiple <glossterm>Relation</glossterm>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-key"> + <glossterm>Key</glossterm> + <glossdef> + <para> + A means of identifying a <glossterm>Row</glossterm> within a + <glossterm>Table</glossterm> or <glossterm>Relation</glossterm> by + values contained within one or more <glossterm>Attribute</glossterm>s + in that <glossterm>Table</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-lock"> + <glossterm>Lock</glossterm> + <glossdef> + <para> + A mechanism that allows a process to limit or prevent simultaneous + access to a resource. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-log-file"> + <glossterm>Log File</glossterm> + <glossdef> + <para> + <glossterm>Log File</glossterm>s contain human-readable text lines about + events. Examples include login failures, long-running queries, etc. + </para> + <para> + For more information, see + <xref linkend="logfile-maintenance"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-logger"> + <glossterm>Logger (process)</glossterm> + <glossdef> + <para> + If activated, the + <glossterm>Logger</glossterm> process + writes information about database events into the current + <glossterm>Log File</glossterm>. When reaching certain time- or + volume-dependent criteria, a new log file is created. + Also called <firstterm>syslogger</firstterm>. + </para> + <para> + For more information, see + <xref linkend="runtime-config-logging"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-log-record"> + <glossterm>Log Record</glossterm> + <glossdef> + <para> + Archaic term for a <glossterm>WAL Record</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-logged"> + <glossterm>Logged</glossterm> + <glossdef> + <para> + A <glossterm>Table</glossterm> is considered + <glossterm>Logged</glossterm> if changes to it are sent to the + <glossterm>WAL Log</glossterm>. By default, all regular + <glossterm>Table</glossterm>s are <glossterm>Logged</glossterm>. A + table can be specified as <glossterm>Unlogged</glossterm> either at + creation time or via the <command>ALTER TABLE</command> command. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-master"> + <glossterm>Master</glossterm> + <glossdef> + <para> + When two or more <glossterm>Database</glossterm>s are linked via + <glossterm>Replication</glossterm>, the <glossterm>Server</glossterm> + that is considered the authoritative source of information is called + the <glossterm>Master</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-materialized"> + <glossterm>Materialized</glossterm> + <glossdef> + <para> + The act of storing information rather than just the method of accessing + the information. This term is used in <glossterm>Materialized + View</glossterm>s, meaning that the data derived from the + <glossterm>View</glossterm> is actually stored on disk separately from + the sources of that data. When using the term + <glossterm>Materialized</glossterm> to refer to + multi-step queries, it means that the data of a given step is stored + in memory, but that storage may spill over onto disk. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-materialized-view"> + <glossterm>Materialized View</glossterm> + <glossdef> + <para> + A <glossterm>Relation</glossterm> that is defined in the same way that + a <glossterm>View</glossterm> is, but stores data in the same way + that a <glossterm>Table</glossterm> does. It cannot be modified via + <command>INSERT</command>, <command>UPDATE</command>, or + <command>DELETE</command> operations. + </para> + <para> + For more information, see + <xref linkend="sql-creatematerializedview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-null"> + <glossterm>Null</glossterm> + <glossdef> + <para> + A concept of non-existence that is a central tenet of Relational + Database Theory. It represents the absence of value. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-partition"> + <glossterm>Partition</glossterm> + <glossdef> + <para> + In reference to a <glossterm>Table</glossterm>: + A <glossterm>Table</glossterm> that can be queried directly, + or via a partitioned table, which is a collection of + sub-tables, each capable of holding one defined + subset of information that does not overlap with any other + table in the collection. + </para> + <para> + In reference to a <glossterm>Analytic Function</glossterm>: + a partition is a definition that identifies which neighboring + <glossterm>Row</glossterm>s can be considered by the + function. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-postmaster"> + <glossterm>Postmaster</glossterm> + <glossdef> + <para> + The very first process of an <glossterm>Instance</glossterm>. It + starts the other processes and creates + <glossterm>Backend Process</glossterm>es on demand. + </para> + <para> + For more information, see + <xref linkend="server-start"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-primary-key"> + <glossterm>Primary Key</glossterm> + <glossdef> + <para> + A special case of a <glossterm>Unique Index</glossterm> defined on a + <glossterm>Table</glossterm> or other <glossterm>Relation</glossterm> + that also guarantees that all of the <glossterm>Attribute</glossterm>s + within the <glossterm>Primary Key</glossterm> do not have + <glossterm>Null</glossterm> values. As the name implies, there can be + only one <glossterm>Primary Key</glossterm> per + table, though it is possible to have multiple + unique indexes that also have no null-capable attributes. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-procedure"> + <glossterm>Procedure</glossterm> + <glossdef> + <para> + A defined set of instructions for manipulating data within a + <glossterm>Database</glossterm>. A <glossterm>Procedure</glossterm> can + be written in a variety of programming languages. They may seem + similar to <glossterm>Function</glossterm>s, but are different in that + they must be invoked via the <command>CALL</command> command rather + than the <command>SELECT</command> or <command>PERFORM</command> + commands, and they are allowed to make transactional statements such + as <command>COMMIT</command> and <command>ROLLBACK</command>. + </para> + <para> + For more information, see + <xref linkend="sql-createprocedure"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Record</glossterm> + <glosssee otherterm="glossary-tuple" /> + </glossentry> + + <glossentry> + <glossterm>Recycling</glossterm> + <glosssee otherterm="glossary-wal-file" /> + </glossentry> + + <glossentry id="glossary-referential-integrity"> + <glossterm>Referential Integrity</glossterm> + <glossdef> + <para> + A means of restricting data in one <glossterm>Relation</glossterm> + by a <glossterm>Foreign Key</glossterm> + so that it must have matching data in another + <glossterm>Relation</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-relation"> + <glossterm>Relation</glossterm> + <glossdef> + <para> + The generic term for all objects in a <glossterm>Database</glossterm> + that have a name and a list of <glossterm>Attribute</glossterm>s + defined in a specific order. <glossterm>Table</glossterm>s, + <glossterm>View</glossterm>s, <glossterm>Foreign Table</glossterm>s, + <glossterm>Materialized View</glossterm>s, and + <glossterm>Index</glossterm>es are all + <glossterm>Relation</glossterm>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-replica"> + <glossterm>Replica</glossterm> + <glossdef> + <para> + A <glossterm>Database</glossterm> that is paired with a + <glossterm>Master</glossterm> + database and is maintaining a copy of some or + all of the Master <glossterm>Database</glossterm>'s data. The primary + reasons for doing this are to allow for greater access to that data, + and to maintain availability of the data in the event that the + <glossterm>Master</glossterm> becomes unavailable. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-replication"> + <glossterm>Replication</glossterm> + <glossdef> + <para> + The act of reproducing data on one <glossterm>Server</glossterm> onto + another server called a <glossterm>Replica</glossterm>. This can take the + form of Physical <glossterm>Replication</glossterm>, where all file + changes from one server are copied verbatim, + or Logical <glossterm>Replication</glossterm> where a defined subset + of data changes are conveyed. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-result-set"> + <glossterm>Result Set</glossterm> + <glossdef> + <para> + A data structure transmitted from a <glossterm>Backend Process</glossterm> to + client program upon the completion of a <acronym>SQL</acronym> + command, usually a <command>SELECT</command> but it can be an + <command>INSERT</command>, <command>UPDATE</command>, or + <command>DELETE</command> command if the <literal>RETURNING</literal> + clause is specified. The data structure consists of zero or more + <glossterm>Row</glossterm>s with the same ordered set of + <glossterm>Attribute</glossterm>s. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-revoke"> + <glossterm>Revoke</glossterm> + <glossdef> + <para> + A command to prevent access to a named set of + <glossterm>Database</glossterm> objects for a named list of + <glossterm>User</glossterm>s and <glossterm>Role</glossterm>s. + </para> + <para> + For more information, see + <xref linkend="sql-revoke"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-role"> + <glossterm>Role</glossterm> + <glossdef> + <para> + A collection of access privileges to the + <glossterm>Database</glossterm>. <glossterm>Role</glossterm>s are + themselves a privilege that can be granted to other roles. This is + often done for convenience or to ensure completeness when multiple + <glossterm>User</glossterm>s need the same privileges. + </para> + <para> + For more information, see + <xref linkend="sql-createrole"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-rollback"> + <glossterm>Rollback</glossterm> + <glossdef> + <para> + A command to undo all of the operations performed since the beginning + of a <glossterm>Transaction</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-rollback"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Row</glossterm> + <glosssee otherterm="glossary-tuple" /> + </glossentry> + + <glossentry id="glossary-savepoint"> + <glossterm>Savepoint</glossterm> + <glossdef> + <para> + A special mark inside the sequence of steps in a + <glossterm>Transaction</glossterm>. Data modifications after this + point in time may be reverted to the time of the savepoint. + </para> + <para> + For more information, see + <xref linkend="sql-savepoint"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-schema"> + <glossterm>Schema</glossterm> + <glossdef> + <para> + A <glossterm>Schema</glossterm> is a namespace for + <glossterm>SQL object</glossterm>s, which all reside in the same + <glossterm>database</glossterm>. Each <glossterm>SQL + object</glossterm> must reside in exactly one + <glossterm>Schema</glossterm>. + </para> + <para> + In general, the names of <glossterm>SQL Object</glossterm>s in the + schema are unique — even across different types of objects. The lone + exception is the case of <glossterm>Unique</glossterm> + <glossterm>Constraint</glossterm>s, in which case there + <emphasis>must</emphasis> be a <glossterm>Unique Index</glossterm> + with the same name and <glossterm>Schema</glossterm> as the + <glossterm>Constraint</glossterm>. There is no restriction on reusing + a name in multiple <glossterm>Schema</glossterm>s. + </para> + <para> + Many <glossterm>SQL Object</glossterm>s reside in the default + <glossterm>Schema</glossterm> <literal>public</literal>, but it is + expected that more schemas are created to hold application-specific + <glossterm>SQL Object</glossterm>s. + </para> + <para> + More generically, the term <glossterm>Schema</glossterm> is used to + mean all data descriptions (<glossterm>Table</glossterm> definitions, + <glossterm>Constraint</glossterm>s, comments) for a given + <glossterm>Database</glossterm>. + </para> + <para> + For more information, see + <xref linkend="ddl-schemas"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>Segment</glossterm> + <glosssee otherterm="glossary-file-segment" /> + </glossentry> + + <glossentry id="glossary-select"> + <glossterm>Select</glossterm> + <glossdef> + <para> + The <acronym>SQL</acronym> command used to query a <glossterm>Database</glossterm>. + Normally, <command>SELECT</command>s are not expected to modify the + <glossterm>Database</glossterm> in any way, but it is possible that + <glossterm>Function</glossterm>s invoked within the query could have + side effects that do modify data. + </para> + <para> + For more information, see + <xref linkend="sql-select"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-serializable"> + <glossterm>Serializable</glossterm> + <glossdef> + <para> + Transactions defined as <literal>SERIALIZABLE</literal> are unable to + see changes made within other transactions. In effect, for the + initializing session the entire <glossterm>Database</glossterm> + appears to be frozen for the duration of the + <glossterm>Transaction</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-server"> + <glossterm>Server</glossterm> + <glossdef> + <para> + The term <glossterm>Server</glossterm> denotes real hardware, a + container, or a Virtual Machine. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-session"> + <glossterm>Session</glossterm> + <glossdef> + <para> + A <glossterm>Connection</glossterm> to the <glossterm>Database</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-sequence"> + <glossterm>Sequence</glossterm> + <glossdef> + <para> + A <glossterm>Database</glossterm> object which represents the + mathematical concept of a numerical integral sequence. It can be + thought of as a <glossterm>Table</glossterm> with exactly one + <glossterm>Row</glossterm> and one <glossterm>Column</glossterm>. The + value stored is known as the current value. A + <glossterm>Sequence</glossterm> has a defined direction (usually + increasing) and an interval step (usually 1). Whenever the + <literal>NEXTVAL</literal> pseudo-column of a + <glossterm>Sequence</glossterm> is accessed, the current value is moved + in the defined direction by the defined interval step, that value + is returned to the invoking query, and the current value of the + sequence is updated to reflect the new value. The value can be updated + multiple times in a single query, the net effect being that each row + selected will have a different value. Values taken from a + <glossterm>Sequence</glossterm> are never reverted, even in the case of + a <glossterm>Rollback</glossterm>, which means that the + <glossterm>Sequence</glossterm> will never generate the same number twice, + which makes it useful for generating + <glossterm>Primary Key</glossterm> values. + </para> + <para> + For more information, see + <xref linkend="sql-createsequence"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-shared-memory"> + <glossterm>Shared Memory</glossterm> + <glossdef> + <para> + <acronym>RAM</acronym> which is used by the processes common to an + <glossterm>Instance</glossterm>. It mirrors parts of + <glossterm>Database</glossterm> files, provides an area for + <glossterm>WAL Record</glossterm>s, and stores additional common + information. Note that <glossterm>Shared Memory</glossterm> belongs to + the complete <glossterm>Instance</glossterm>, not to a single + <glossterm>Database</glossterm>. + </para> + <para> + <glossterm>Shared Memory</glossterm> is organized into pages. If a + page is modified, it is called a dirty page until it is written back + to the file system. + </para> + <para> + For more information, see + <xref linkend="runtime-config-resource-memory"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-sql-object"> + <glossterm>SQL Object</glossterm> + <glossdef> + <para> + A <glossterm>Table</glossterm>, <glossterm>View</glossterm>, + <glossterm>Materialized View</glossterm>, + <glossterm>Index</glossterm>, <glossterm>Constraint</glossterm>, + <glossterm>Sequence</glossterm>, <glossterm>Function</glossterm>, + <glossterm>Procedure</glossterm>, <glossterm>Trigger</glossterm>, + data type, or operator. Every <glossterm>SQL Object</glossterm> + belongs to exactly one <glossterm>Schema</glossterm>. + </para> + <para> + For more information, see + <xref linkend="manage-ag-overview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-stats-collector"> + <glossterm>Stats Collector</glossterm> + <glossdef> + <para> + This process collects statistical information about the + <glossterm>Cluster</glossterm>'s activities. + </para> + <para> + For more information, see + <xref linkend="monitoring-stats"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-system-catalog"> + <glossterm>System Catalog</glossterm> + <glossdef> + <para> + A collection of <glossterm>Table</glossterm>s and + <glossterm>View</glossterm>s which describe the structure of all + <acronym>SQL</acronym> objects of the <glossterm>Database</glossterm> + and the <glossterm>Global SQL Object</glossterm>s of the + <glossterm>Cluster</glossterm>. The <glossterm>System + Catalog</glossterm> resides in the schema + <literal>pg_catalog</literal>. Main parts are mirrored as + <glossterm>View</glossterm>s in the <glossterm>Schema</glossterm> + <literal>information_schema</literal>. + </para> + <para> + For more information, see + <xref linkend="ddl-schemas"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-table"> + <glossterm>Table</glossterm> + <glossdef> + <para> + A collection of <glossterm>Tuple</glossterm>s (also known as + <glossterm>Row</glossterm>s or <glossterm>Record</glossterm>s) having + a common data structure (the same number of + <glossterm>Attribute</glossterm>s, in the same order, having the same + name and type per position). A <glossterm>Table</glossterm> is the + most common form of <glossterm>Relation</glossterm> in + <productname>PostgreSQL</productname>. + </para> + <para> + For more information, see + <xref linkend="sql-createtable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-tablespace"> + <glossterm>Tablespace</glossterm> + <glossdef> + <para> + A named location on the server filesystem. All <glossterm>SQL Object</glossterm>s + which require storage beyond their definition in the + <glossterm>System Catalog</glossterm> + must belong to a single tablespace. + </para> + <para> + For more information, see + <xref linkend="manage-ag-tablespaces"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-temporary-tables"> + <glossterm>Temporary Table</glossterm> + <glossdef> + <para> + <glossterm>Table</glossterm>s that exist either for the lifetime of a + <glossterm>Session</glossterm> or a + <glossterm>Transaction</glossterm>, as specified at the time of creation. The + data in them is not visible to other sessions, + and is not <glossterm>Logged</glossterm>. + <glossterm>Temporary Table</glossterm>s are often used to store + intermediate data for a multi-step operation. + </para> + <para> + For more information, see + <xref linkend="sql-createtable"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-transaction"> + <glossterm>Transaction</glossterm> + <glossdef> + <para> + A combination of commands that must act as a single + <glossterm>Atomic</glossterm> command: they all succeed or all fail + as a single unit, and their effects are not visible to other + <glossterm>Session</glossterm>s until + the <glossterm>Transaction</glossterm> is complete. + </para> + <para> + For more information, see + <xref linkend="transaction-iso"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-trigger"> + <glossterm>Trigger</glossterm> + <glossdef> + <para> + A <glossterm>Function</glossterm> which can be defined to execute + whenever a certain operation (<command>INSERT</command>, + <command>UPDATE</command>, <command>DELETE</command>, + <command>TRUNCATE</command>) is applied to a <glossterm>Relation</glossterm>. + A <glossterm>Trigger</glossterm> + executes within the same <glossterm>Transaction</glossterm> as the + statement which invoked it, and if the <glossterm>Function</glossterm> + fails, then the invoking statement also fails. + </para> + <para> + For more information, see + <xref linkend="sql-createtrigger"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-tuple"> + <glossterm>Tuple</glossterm> + <glossdef> + <para> + A collection of <glossterm>Attribute</glossterm>s in a fixed order. + That order may be defined by the <glossterm>Table</glossterm> where + the <glossterm>Tuple</glossterm> is found, in which case the + <glossterm>Tuple</glossterm> is often called a + <glossterm>Row</glossterm> or <glossterm>Record</glossterm>. It may + also be defined by the structure of a + <glossterm>Result Set</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-unique"> + <glossterm>Unique</glossterm> + <glossdef> + <para> + The condition of having no duplicate values in the same + <glossterm>Column</glossterm> of a <glossterm>Relation</glossterm>. + Often used in the concept of + <glossterm>Unique Index</glossterm>es. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-unlogged"> + <glossterm>Unlogged</glossterm> + <glossdef> + <para> + Changes to an unlogged <glossterm>Relation</glossterm> are not + reflected in the <glossterm>WAL Log</glossterm>. This disables + replication and crash recovery for these relations. + </para> + <para> + The primary use of unlogged tables is for storing + transient work data that must be shared across processes. + </para> + <para> + <glossterm>Temporary Table</glossterm>s are always unlogged. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-update"> + <glossterm>Update</glossterm> + <glossdef> + <para> + A <acronym>SQL</acronym> command used to modify <glossterm>Row</glossterm>s + that may already exist in a specified <glossterm>Table</glossterm>. + It cannot create or remove rows. + </para> + <para> + For more information, see + <xref linkend="sql-update"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-user"> + <glossterm>User</glossterm> + <glossdef> + <para> + A <glossterm>Role</glossterm> that has the <literal>LOGIN</literal> + privilege is said to be a <glossterm>User</glossterm>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-user-mapping"> + <glossterm>User Mapping</glossterm> + <glossdef> + <para> + The translation of login credentials in the local + <glossterm>Database</glossterm> to credentials in a remote data system + defined by a <glossterm>Foreign Data Wrapper</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createusermapping"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-vacuum"> + <glossterm>Vacuum</glossterm> + <glossdef> + <para> + The process of removing outdated <acronym>MVCC</acronym> + <glossterm>Tuple</glossterm>s from a <glossterm>Heap</glossterm> or + <glossterm>Index</glossterm>. This can be initiated through the use of + the <command>VACUUM</command> command, but can also be handled automatically + via <glossterm>Autovacuum</glossterm> processes. + </para> + <para> + For more information, see + <xref linkend="sql-vacuum"/> . + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-view"> + <glossterm>View</glossterm> + <glossdef> + <para> + A <glossterm>Relation</glossterm> that is defined by a + <command>SELECT</command> statement, but has no storage of its own. + Any time a query references a <glossterm>View</glossterm>, the + definition of the <glossterm>View</glossterm> is substituted into the + query as if the user had typed that subquery instead of the name of + the <glossterm>View</glossterm>. + </para> + <para> + For more information, see + <xref linkend="sql-createview"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal-archiver"> + <glossterm>WAL Archiver (process)</glossterm> + <glossdef> + <para> + A process that saves copies of <glossterm>WAL File</glossterm>s + for the purposes of creating backups or keeping + <glossterm>Replica</glossterm>s current. + </para> + <para> + For more information, see + <xref linkend="continuous-archiving"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal-file"> + <glossterm>WAL File</glossterm> + <glossdef> + <para> + Each of the numerically-numbered files that provide storage space for + <glossterm linkend="glossary-wal">WAL</glossterm>. + The files are all of the same predefined size + and are written in sequential order, interspersing changes + as they occur in multiple simultaneous sessions. + If the system crashes, the files are read in order, and each of the + changes are replayed to restore the system to the state as it was + before the crash. + </para> + <para> + Each WAL file can be released after a + <glossterm linkend="glossary-checkpoint">checkpoint</glossterm> + writes all the changes in it to the corresponding data files. + Releasing the file can be done either by deleting it, or by changing its + name so that it will be used in the future, which is called + <firstterm>recycling</firstterm>. + </para> + + <para> + For more information, see + <xref linkend="wal-internals"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>WAL</glossterm> + <glosssee otherterm="glossary-wal" /> + </glossentry> + + <glossentry id="glossary-wal-record"> + <glossterm>WAL Record</glossterm> + <glossdef> + <para> + A low-level description of an individual data change. + It contains sufficient information for the data change to be + re-executed (<firstterm>replayed</firstterm>) in case a system failure + causes the change to be lost. + WAL records use a non-printable binary format. + </para> + <para> + For more information, see + <xref linkend="wal-internals"/>. + </para> + </glossdef> + </glossentry> + + <glossentry> + <glossterm>WAL Segment</glossterm> + <glosssee otherterm="glossary-wal-file" /> + </glossentry> + + <glossentry id="glossary-wal-writer"> + <glossterm>WAL Writer (process)</glossterm> + <glossdef> + <para> + A process that writes <glossterm linkend="glossary-wal-record">WAL records</glossterm> + from <glossterm id="linkend-shared-memory">shared memory</glossterm> to + <glossterm id="linkend-wal-file">WAL files</glossterm>. + </para> + <para> + For more information, see + <xref linkend="runtime-config-wal"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-window-frame"> + <glossterm>Window frame</glossterm> + <glossdef> + <para> + In a result set, a subset of neighboring rows that match some user + specified criteria form a window frame. + For example, in a query that returns employees across several departments, + the employees from each specific department can form one window frame. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-window-function"> + <glossterm>Window Function</glossterm> + <glossdef> + <para> + A type of <glossterm linkend="glossary-function">function</glossterm> whose + result is based on values found in + <glossterm linkend="glossary-tuple">rows</glossterm> of the same + <glossterm linkend="glossary-window-frame">window frame</glossterm>. + All <glossterm linkend="glossary-aggregate">aggregate functions</glossterm> + can be used as window functions, but window functions can also be + used to, for example, give ranks to each of the rows in the window frame. + Also known as <firstterm>analytic functions</firstterm>. + </para> + <para> + For more information, see + <xref linkend="tutorial-window"/>. + </para> + </glossdef> + </glossentry> + + <glossentry id="glossary-wal"> + <glossterm>Write-Ahead Log</glossterm> + <glossdef> + <para> + The journal that keeps track of the changes in the + <glossterm>Instance</glossterm> as user- and system-invoked + operations take place. It comprises many individual + <glossterm linkend="glossary-wal-record">WAL records</glossterm> written + sequentially to <glossterm linkend="glossary-wal-file">WAL files</glossterm>. + </para> + </glossdef> + </glossentry> + </glosslist> +</appendix> diff --git a/doc/src/sgml/postgres.sgml b/doc/src/sgml/postgres.sgml index 1f7bd32878..ba3d626102 100644 --- a/doc/src/sgml/postgres.sgml +++ b/doc/src/sgml/postgres.sgml @@ -278,6 +278,7 @@ &docguide; &limits; &acronyms; + &glossary; &color; </part>
